cite one thing the witches tell macbeth about the future that seems impossible to believe

The second and third apparitions are difficult to believe. The second apparition is a bloody child, who tells him that "none of woman born / Shall harm Macbeth" The third apparition is a crowned child with a tree in its hand, who says that "Macbeth shall never vanquished be until / Great Birnam Wood to high Dunsinane Hill / Shall come against him". This cheers Macbeth even more, since he knows that nothing can move a forest.